Support cradle for rolled coils and other cylindrical objects

ABSTRACT

A cradle unit for supporting metal coils, and other cylindrical objects, consists of two, parallel and separate saddles made of polyurethane or other material having a hardness range of between 50 Shore A and 90 Shore D, which saddles are connected together via a pair of parallel steel angle-brackets that provide inherent structural integrity to the cradle unit itself, while still allowing the unit to conform to the shape or level of the underlying support structure. The single cradle unit may be as a mobile support-device, or may be bolted or otherwise attached to a surface for a specific location of the stored product. The cradle unit is generally concave-shaped and has a first main or central lower concave curvature of a first radius, and a middle or secondary transitional curvature that connects the first main lower curvature to an upper, tertiary concave curvature of a second radius greater than the first radius, so that coils or rolls of different diameter may be safely and firmly supported. In a modification, a pair of rails are provided for fixedly mounting and supporting a plurality of support cradles, where each support cradle is held in place by the rails via metal pins protruding or projecting from the bottom surface of the support cradle that are received in openings formed the rails, whereby no lateral or longitudinal movement or sliding of the support cradles is possible.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional application of application Ser.No. 11/428,623, filed Jul. 5, 2006, and now U.S. Pat. No. 7,708,155,which is a continuation-in-part of application Ser. No. 11/208,953,filed on Aug. 22, 2005, now U.S. Pat. No. 7,448,505.

BACKGROUND OF THE INVENTION

The present invention is directed to a cradle unit, or supportingmember, for supporting and storing coils, such as wound rolls or coilsof long lengths of thin flat material made of steel, other metal, paper,or the like, which are processed, handled, stored and transported withthe longitudinal axis of the coil oriented in the horizontal direction.When stored in their semi-finished, in-process stage between operations,in their finished state awaiting shipment, or during actual shipment andfinal storage during actual use, these coils are placed in designatedstaging areas by supporting them on the floor, since allowing thesecoils to rest directly on the floor or other flat surface would producehighly-stressed loading at the tangential contact points. Even thoughthese coils may be made of metal, they are relatively soft or pliable,and susceptible to damage from scratching, denting or surface-markingwhen they impinge upon debris on the floor or on another hard storagesurface.

Many locations where coils are stored are on floors that are not flat,tending to misshape or deform the coil over time. Coils may also bedamaged from flattening or denting when set down during handlingoperations, or from excessive pressure or weight while sitting instorage due to single-point tangential and high surface-loading. Thissituation is exacerbated when coils are stacked during storage, which iscommon in the metals industries. Therefore, significant expense isincurred from the lost metal and rework of the damaged coils.Additionally, stacked coils, when stored on flat floors, represent asafety hazard from roll out of the bottom tier of the stack. Thissituation is hazardous to personnel, the facilities and the coils thatwould be affected by such a collapse of the stack.

There have been used a number of various techniques in an attempt toaddress the above-mentioned problems. Some of these techniques include:setting coils on rubber or fabric belting; using rubber or polyurethanepads with slight indentations to cradle the coil; using “V”-shapedblocks made of polyurethane, plastic, wood or metal; and unitized skidsof plastic, wood or metal, or other similarly constructed devices tocontain or protect the coils.

Polyurethane, rubber and plastic coil-support devices possess theability to cushion the coil during set-down. These devices are typicallymolded or formed into a single unit, and do not provide suitablestrength or structural integrity to support stacks of coils without theuse of additional, independent, and separate support structures. Woodsupports are not resilient or durable, while metal fabricated supportsdo not cushion and offer a surface that has is basically the same as abare floor. Unitized fabrications of wood, plastic or steel areexpensive to build, do not offer the durability and protection of aresilient support, and do not conform or adapt to uneven floorconditions.

An example of a prior-art support is disclosed in U.S. Pat. No.4,503,978—Smit, et al., and discloses a support for rolled coils made ofpolyethylene. The supports of this patent do not generally provideadequate structural support, and, therefore, are typically supported byU-shaped steel channels bolted to the floor, or other supportingsurfaces, and are generally not conformable to a supportunder-structure.

SUMMARY OF THE INVENTION

It is, therefore, the primary objective of the present invention toprovide a support cradle for coils, rolls, or other cylindrical objectsthat provides its own inherent structural integrity for solelysupporting a coil thereon, while also conforming to the under-structureupon which it is rests, which support cradle may be used to supportcoils or rolls of different diameter.

It is, also, the primary objective of the present invention to providesuch a support cradle that provides its own inherent structuralintegrity for supporting a coil thereon, while also conforming to theunder-structure upon which it is secured, which support may also beconnected to other like-cradles for forming a multi-unit cradle-supportfor supporting a series of coils thereon, while still maintaining itsconforming characteristics for preventing damage to the coils supportedthereon, and for safely stacking of rows of coils thereabove.

In it, also, the primary objective of the present invention to provide apair of rails for fixedly mounting and supporting a plurality of supportcradles, where each support cradle is held in place by the rails viametal pins protruding or projecting from the bottom surface of thesupport cradle that are received in openings formed the rails, while therails themselves are affixed to the floor, whereby no lateral orlongitudinal movement or sliding of the support cradles is possible.

In accordance with the invention, the cradle unit for supporting metalcoils, and other cylindrical objects, consists of two parallel andseparate cradle-sections or saddles made of polyurethane, or othermaterial, having a hardness range of between 50 Shore A and 90 Shore D,which cradle-sections are joined or connected together via a pair ofparallel steel angle-brackets that provide inherent structural integrityto the cradle unit itself, while still allowing the saddles to conformto the shape or level of the underlying support structure, whereby aplurality of cradle units may be used for supporting coils in a tieredstack. The single cradle unit may be used as a mobile support-device, ormay be bolted or otherwise attached to a surface for a specific locationof the stored product. The cradle unit of the invention may, also, beattached to the bed of a transportation vehicle, such as a truck traileror rail car, in order to provide secure, protective storage and locationof the items. In this case, the nature of the resilient or soft materialfrom which the cradle unit is made provides shock-absorption qualitiesfor the transported coil.

The cradle unit generally defines a concave-shaped upper surface, andhas a first main or central lower concave curvature of a first radius, apair of middle or secondary transitional curvature-sections that connectthe first main lower curvature to a pair of upper, tertiary concavecurvature-sections of a second radius greater than the first radius, sothat coils or rolls of different diameter may be safely and firmlyaccommodated.

In a modification of the invention, a multiple-unit version is providedwhere a series of cradle units of the invention are connected togetherto form one elongated integral support structural unit. Thismodification is a unitized rack that forms a row-storage arrangementwhere the stored coils or objects are stored randomly along the lengthof the rack, for securing and protecting the stored coils or objects,with the coils arranged lengthwise along the length of the rack.

In another modification, each cradle unit is provided withoutwardly-projecting oil-receiving pans or reservoirs for collecting oilor other liquid lubricant seeping or draining out from the ends of thecoil supported thereby. These pans provide for the containment of thefluid to prevent contamination of the surrounding environment, andprovide for safe, easy recovery and disposal of the liquid.

In yet another modification, a plurality of support cradles are looselymounted in place to a pair of rails which, in turn, is affixed to afloor in order to prevent sliding of the support cradles while allowingfor flexing of the support cradles under full-load conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood with reference to theaccompanying drawings, wherein:

FIG. 1 is an isometric view of the cradle unit for supporting a coil,roll, or other cylindrical object in accordance with the invention;

FIG. 2 is a top view thereof.

FIG. 3 is a side, elevational view thereof;

FIG. 4 is an end view thereof;

FIG. 5 is an isometric view showing a series of cradle units of FIG. 1being used to support a tiered stack of coils or rolls;

FIG. 6 is an isometric view similar to FIG. 5 showing the force vectorsacting on the coils or rolls and on the series of cradle unitssupporting the stack of coils or rolls;

FIG. 7 is an isometric view of a modification in which a series ofcradle units of FIG. 1 are provided in one unitary structure for forminga rack for supporting a series of coils, rolls, or other cylindricalobjects in a row;

FIG. 8 is an end view thereof;

FIG. 9 is a side elevational view thereof;

FIG. 10 is an isometric view showing a series of cradle racks of FIG. 7being used to support a plurality of stacked rows of coils or rolls;

FIG. 11 is an isometric view of another modification of the cradle unitof FIG. 1 with the addition of a pair of end-pans serving as reservoirsfor collecting lubricant draining from coils or rolls supported orstacked thereon;

FIG. 12 is a side elevational view thereof;

FIG. 13 is a top view thereof;

FIG. 14 is an end view thereof;

FIG. 15 is a side view of yet another modification of the cradle unitwhere each the cradle unit is provided with protruding metal pins forreception in openings of a pair of rails affixed to a floor, or thelike, by which the cradle unit is retained in place and prevented fromsliding movement;

FIG. 16 is a top view thereof;

FIG. 17 is an end view thereof;

FIG. 18 is a top plan view of a rail fixable to a floor or otherunderstructure to a pair of which rails a cradle unit of FIG. 15 issecured;

FIG. 19 is a top plan view of a pair of rails of FIG. 18 affixed to afloor or other understructure and shown supporting and securing aplurality of cradle units of FIG. 15 in a spaced apart manner via theprotruding metal pins of the cradle units received in openings of therails; and

FIG. 20 is a side elevational view of FIG. 19.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings in greater detail, and to FIGS. 1-6 fornow, there is shown a cradle unit 10 of the invention for supporting acoil, roll, or other large cylindrical object. The cradle unit 10consists of a pair of parallel-arranged, identical end-cradle sectionsor saddles 12, 14 preferably made of polyurethane, in the hardness rangeof between 50 Shore A and 90 Shore D. The length of each end-cradlesection or saddle 12, 14 depends upon the size or sizes of the coils orrolls to be supported. In one example, each end-cradle section is thirtythree inches in length and three inches in width. Each end-cradlesection or saddle 12, 14 defines an upwardly-facing concave supportingsurface 16, 18 which consists of a first lower or main portion 16′, 18′,respectively, having a first radius R1, and second upper or tertiary endportions 16″, 18″ each having a second radius R2 that is greater thanthe radius R1. Connecting the surface-portion 16′ or 18′ with theportions 16″ or 18″ are transitional curvature-portions or regions 20,22, respectively. The values of R1 and R2 will vary depending upon thesize of coils or rolls to be supported. The value R1 corresponds to theradius of the minimal coil or roll to be supported by the cradle 10,while the value R2 corresponds to the radius of the maximal coil or rollto be supported by the cradle 10. In the example given above, the firstradius R1 is twenty inches, while the second radius R2 is thirty sixinches, with the height of each end-cradle section or saddle increasingfrom a minimum of one inch at the midpoint or center to a maximum offive inches at the extremity or end 24, 26.

With regard to the transitional regions 20, 22, it is noted that thefirst lower or main portion 16′, 18′ and the second upper or tertiaryend portions 16″, 18″ not only have different radii R1 and R2, but, ofcourse, also have different points of centers pt1 and pt2, respectively.The shape or curvature of each transition region 20, 22 is formed bygenerating a number of circles of different radii and from a varyingcenter position pt[i] between the center points pt1 and pt2 in a linearrelationship. Using the equation:pt[i]=pt1+(pt2−pt1)/(r2−r1)*abs(r1−r[i]), where pt[i] is a center pointof a transitional circle and r[i] is the radius of the transitionalcircle, connecting the tangents of these generated circles form thecurve of each transition region 20, 22.

The cradle unit 10 also includes a pair of parallel-arranged steelangle-brackets 30, 32 which provide the inherent structural integrity tothe unit. Each angle-bracket connects corresponding ends of the twoend-cradle sections 12,14, as seen in FIG. 1. Each angle-bracket 30, 32consists of a horizontal section 34 and a vertical section 36, with arespective end of a cradle unit being nestled therein. The right-anglebrackets are bonded to the ends of the end-cradle sections byconventional bonding techniques, whereby a flexible and adaptablerectilinear-shaped structure is formed. In the above-mentioned example,the length of each angle bracket may be typically thirty-six inches,with the width of each of the horizontal and vertical sections typicallybeing three inches, and typically made of 3/16″ steel. Each horizontalsection 34 may be provided with a pair of holes 46 for passingtherethrough bolts for securing the cradle unit 10 to a floor or otherunder-structure.

Referring to FIGS. 5 and 6, it may be seen how a series of cradle units10 may be used to support a tiered vertical stack of rows of coils orrolls 40. The force vector diagram depicts coils C1 through C8 stackedon the coil cradle units 10 of the invention. The loads are calculatedas if the stack continues on to the left of the diagram. Each coil shownhas been assumed to be of a 72″ O.D. and a weight W. Because of thestacking, the downward force W splits into the two vector forces W_(L)and W_(R). For purposes of clarity, only coil C2 has been shown with theforces labeled. On the middle row, the forces acting on coil C4 are itsweight W plus W_(R) from coil C1 and W_(L) from coil C2. The resultantforce, 2·W, is drawn using vector addition. The forces acting on coil C5are its weight W plus W_(R) from coil C2. The resultant force is drawnusing vector addition. On the bottom row, the forces acting on coil C6are its weight W plus 2·W_(R) from coil C3 and 2·W_(L) from coil C4. Theresultant force, 3·W, is drawn using vector addition. The forces actingon coil C7 are its weight W plus 2·W_(R) from coil C4 and W_(L) fromcoil C5. The resultant force is drawn using vector addition. The forcesacting on coil C8 are its weight W plus 2·W_(R) from coil. The resultantforce is drawn using vector addition. On the bottom row, lines are drawnfrom the center of the coils to the edges of the ends 24, 26 of thecradle units. If the resultant force vectors remain in between theselines, the stack will be stable, assuming that the coils in the stackare frictionless and not considering inertia. In actual use, the stackcould be stable even if this limit were somewhat exceeded. Because ofthe provision of two separate upper curved sections of different radiiR1 and R2 for each cradle unit, multiple layers of coils of differentdiameter may be more safely stacked, as shown in FIGS. 5 and 6.

Referring now to FIGS. 7-10, there is a shown a modification in which aseries of cradle units 10 are provided to form a rack 50 of cradles forsupporting a plurality of individual coils thereon end-to-end to form aladder-like structure. The rack 50 consists of a plurality of cradleelements 52 similar to the end-cradle sections 12, 14 of the cradle unit10, which cradle sections 52 are interconnected together by a pairelongated steel angle-brackets 54, 56 similar to the angle-brackets 30,32 of the cradle unit 10 of FIG. 1. The spacing between the cradleelements 52 is generally less than the spacing between the end-cradlesections or saddles 12, 14 of the cradle unit 10. Whereas the spacingbetween the cradle sections 12, 14 in one example cited above is thirtyinches, the spacing between adjacent cradle elements 52 is 15¼ inches,so that, not only variously-sized rolls or coils of different diametersmay be supported and stored on the rack 50, but also coils or rolls ofdifferent lengths may be supported thereby. In addition, owing to theseries arrangement of cradle sections 52, the placing of a coil or rollon the rack 50 may be achieved at any portion along the length thereofthereby allowing facility of placement and storage. A plurality of racks50 may be employed in parallel formation, as shown in FIG. 10, in orderto allow for support and storage of multiple, stacked rows of coils orrolls 40. The spacing between racks 50 is dependent upon the size of thecoils or rolls 40 to be supported. Each individual rack 50 is bolted tothe floor or under-structure by bolts passing through the anglebrackets, in the same manner described above with reference to thecradle unit 10. In addition, oil pans similar to oil pans describedhereinbelow with reference to FIGS. 11-14, may also be used forcollecting oil, or other fluid. It is noted that the individual rolls orcoils are supported end-to-end, with their longitudinal axes beingparallel to the length of the rack, whereby the rack 50 supports them inthe manner that has hithertofore only been done using a coil pad. Thus,the rack 50 serves the dual function of acting as cradle supports and asa coil pad.

Referring now to FIGS. 11-14, there is shown another modification 60 ofthe cradle unit 10 in which a pair of oil-collecting pans or reservoirs62, 64 are provided at the ends of the cradle unit in order to collectoil or other lubricant or fluid seeping or draining out from the ends ofthe coil supported thereby. These pans provide for the containment ofthe fluid to prevent contamination of the surrounding environment, andprovide for safe, easy recovery and disposal of the liquid. Eachoil-collection pan 62, 64 is preferably formed integrally with therespective cradle section 12, 14, and typically has a width of twelveinches and a length of two feet. Each pan 62, 64 is provided with anupstanding lip or rim 62′, 64′ for containing the oil. The rest of thecradle unit 60 is substantially identical to the cradle unit 10.

The cradle of the invention adapts readily and inherently to the contourof the underlying support structure or floor, with the spacing betweenthe angle-brackets and between the saddles providing a self-adaptingunitary structure, so that uneven or contoured floors will not adverselyaffect the support provided by the cradle of the invention. Moreover,the inherent resiliency of the material used in the saddles offershock-absorption characteristics.

While the preferred material for the saddles has been indicated as beingpolyurethane, other, comparable or equivalent material may be usedinstead, or composites thereof, as long as these other materials arewithin the same hardness range of between 50 Shore A and 90 Shore D.Some of these other materials are, for example: nylon; nyrim;polyethylene of all molecular weights (ultra high, high density, mediumdensity, low density, copolymers, homopolymers); rubber such as SBR,EPDM, nitrile, Neoprene (polychloroprene), natural, Hypalon(chlorosulfonated polyethylene rubber), butyl; granulated and rebondedrubber; and recycled plastics; recycled plastic/wood flour or othersimilarly formulated blends; polypropylene; vinyl (PVC).

While specific dimensions have been given hereinabove, it is to beunderstood that these have been given only by way of example. The actualdimensions may vary depending upon the lengths and diameters of thecoils or rolls intended to be supported.

While the transition regions 20, 22 have been described as having shapeor contour described hereinabove, it is to be understood that othermethods for producing the shape or contour thereof may employed, as wellother different shapes and curvature.

In a variation of the support cradle, the end-cradle section or saddle12, 14 defines an upwardly-facing concave supporting surface 16, 18which consists of a first lower or main portion 16′, 18′, respectively,having a first radius R1 of about 18 inches, second upper or tertiaryend portions 16″, 18″ each having a second radius R2 of about 36 inches,with the height of each end-cradle section or saddle increasing from aminimum of 1½ inches at the midpoint or center to a maximum of 8½ inchesat the extremity or end 24, 26.

Referring now to FIGS. 15-20, there is shown another modification 68 ofthe cradle unit. This version has especial relevance for the storage ofcoils, rolls, and the like, on the floor of a truck duringtransportation thereby, although it is intended for use in all storageenvironments and locations, whether mobile or fixedly stationary. Inorder to take into account moments and forces tending to dislodge ordisplace the support cradles during normal use and loading, there areprovided at least one pair of longitudinal rails mounted to the floor ofthe truck, as shown in FIGS. 18-20. The pair of rails 70, 72 are spacedapart on the floor or other understructure by a distance thataccommodates the width of the support cradle unit 68, which width isdefined in the direction between the saddles 82 of the cradle unit oralternatively by the length of each connecting brace 90, 92.

In the preferred embodiment, this spacing is either thirty or thirty-sixinches, as taken between the outer surfaces 70′, 72′ of the rails. Eachrail 70, 72 is provided with a first series of pairs of holes oropenings 76, 78 by which screws or bolts permanently affix the rails afloor. There are also provided a second series of equally-spaced apartholes or openings 80 by which support cradles are connected to therails. The cradle unit 68 is similar to the saddle units of the otherembodiments described hereinabove, with the exception of the addition ofa pair of spaced-apart metal pins 84, 86 formed in each of the cradlesections or saddles 82. Each metal pin 84, 86 has a projecting orprotruding bottom section 84′, 86′ provided in and projecting from thebottom surface 82′ of a saddle 82, which projecting sections 84′, 86′are received in respective openings of the series of the openings 80 ofthe rails 70, 72. The openings 80 are of a larger diameter than that ofthe pins 84, 86 so that the protruding bottom sections 84′, 86′ areloosely received in the holes 80 in order to allow a limited degree ofmovement. This loose mounting of the pins in the openings 80 is donebecause, during normal loading of the support cradles with coils, thecradle units experience flexing and bending whereby the distance betweenthe center lines of the pins 84, 86 tend to change, This loose fittingaccommodates such flexing and bending. In the preferred embodiment, eachmetal pin 84, 86 is approximately 4 7/16 inches in length and has adiameter of approximately ⅞ of an inch, with a projecting portion 84′,86′ that project outwardly from the bottom surface 82′ of approximately7/16 of an inch. Each metal pin is mounted in a respective saddle byfirst drilling a hole, and then inserting and adhesively securing a pinin the hole. In the preferred embodiment, the holes 80 of the railelements have a diameter of approximately 1 1/16 inches, which, giventhe ⅞ inch diameter of each metal pin 84, 86, allows an approximately1/16 of an inch play or movement of the pin in a hole, which is morethan adequate to allow for the changes in spacing between pins 84 or 86during flexing and bending under full-load conditions. As mentionedabove, the spacing between the two fixed rails 70, 72 is equal to thewidth of the cradle unit 68.

Also in the preferred embodiment, the length of each rail isapproximately 239⅞ inches a width of three inches, and a thickness of ½inch. The spacing between holes 80 is approximately five inches, centerto center. Also in the preferred embodiment, the spacing between thepins of one saddle and the spacing between the pins of the other saddleare approximately thirty inches, center to center. The width of thecradle unit may be approximately 30 inches or 36 inches, which is equalto length of each of the parallel-arranged steel braces 90, 92. It is,also, noted that in this modification, the parallel-arranged steelbraces 90, 92 are not angle-brackets, as in the other embodimentsdescribed above, but are just straight elements connecting the pair ofsaddle supports 82 at portions of the saddle supports above the bottomsurfaces 82′ thereof, so that the projecting pins 84, 86 may be used formounting the cradle unit 68 in the rails 70, 72, in the manner describedhereinabove.

Also, in the preferred embodiment, the radius R1 for cradle unit 68 iseighteen inches and the radius R2 is thirty-six inches. The transitionregion is determined using the same method described hereinabove withreference to the embodiment of FIG. 1.

While the pins 82, 84 have been indicated as being metal, it is to beunderstood that other, equivalent materials may be used. In addition,the above-listed dimensions have been given only by means of example andare not to be construed to be limiting. Moreover, while the projectingmembers have been described as pins, other equivalent members may beused instead, it being understood that the projecting members are not tobe construed to exclude other equivalent members or manners for mountingthe saddles in the holes of the rail elements for a limited degree ofmovement therein.

While specific embodiments of the invention have been shown anddescribed, it is to be understood that numerous changes andmodifications may be made therein without departing from the scope andspirit of the invention as set forth in the appended claims.

1. A method of supporting a plurality of support cradles used insupporting coils, rolls, and other cylindrical objects, where eachsupport cradle comprises a pair of parallel saddle elements where eachsaddle element comprises a bottom surface and projecting membersprojecting from the bottom surface, with each said saddle elementcomprising a concave upper surface defining a central, lower curvedsection, and a pair of parallel connecting elements each connectingcorresponding sections of said pair of saddle elements in order to forma rectilinear-shaped structure, said method comprising: (a) affixing apair of spaced-apart rail elements to an understructure in a spacedapart manner, where each rail element comprises an upper surface havinga series of linearly-arranged holes along a portion of the lengththereof; (b) loosely attaching a plurality of said support cradles in alinear series to the rail elements of said step (a) such that eachsupport cradle is supported by the pair of rail elements; (c) said step(b) comprising inserting the respective projecting members projectingfrom the respective bottom surface of one parallel saddle element ofeach said support cradle into respective chosen holes of the series ofholes of one of the pair of rail elements; (d) said step (b) furthercomprising inserting the respective projecting members projecting fromthe respective bottom surface of the other parallel saddle element ofeach support cradle into respective chosen holes of the series of holesof the other of the pair of rail elements; (e) said step (c) comprisinginserting the respective projecting members into respective holes suchthat said projecting members are allowed a limited degree of movement inthe holes in order to accommodate distortions induced in said supportcradle under load conditions.
 2. The method according to claim 1,wherein each support cradle comprises a width and each connectingelement comprises a length, the width of a support cradle beingapproximately equal to the length of a connecting element of a saidsupport cradle.
 3. The method according to claim 1, wherein said step(b) comprises repeating said step (c) a plurality of times for mountinga plurality of support cradles to the pair of rail elements, whereineach said step (c) comprises inserting the respective projecting membersinto a series of holes equally-spaced along respective upper surfaces ofsaid rail elements, each said hole of said series of holes having a sizegreater than the size of a said projecting member so that a respectiveprojecting member is allowed movement therein, whereby the projectingmembers of a respective saddle element may be received in a number ofdifferent holes of a respective rail element for allowing differentspacing between support cradles.